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Biomedical subjects

R J Maughan

Publications and source records attributed to R J Maughan.

At least 145 records · Page 8Linked to original sources
PubMed1985

Variability in the response of different male subjects to the effect of marathon running on the increase in plasma high density lipoprotein.

The acute effects of running a 42.2 km marathon race on the concentration and composition of the plasma lipoproteins were studied in 56 men of varying fitness, training experience, age and physical characteristics. There was no change in the mean concentration of total serum cholesterol, but a 10.9% increase (P less than 0.001) in the mean concentrations of high-density lipoprotein cholesterol (HDL-TC), representing an 11.1% increase (P less than 0.001) in the cholesteryl ester (CE) and 9.9% increase (P less than 0.001) in the unesterified cholesterol (UC) moieties of HDL. The ratio of total serum cholesterol to HDL-TC decreased significantly (P less than 0.001) during the exercise. Changes in lipoprotein concentrations during the marathon varied considerably between individual subjects, with a small proportion of subjects exhibiting relatively large increases or decreases in HDL-TC, HDL-CE and HDL-UC. Small sub-populations of runners were identified who showed abnormally large decreases in HDL-UC and abnormally small increases in HDL-CE relative to HDL-UC. A correlation (P less than 0.05) was found between the average weekly mileage of training and the increase in HDL-TC, whilst faster runners (finishing time less than 3 h; n = 13) had a significantly greater (P less than 0.02) increase in HDL-TC than slower runners (greater than 4 h; n = 14).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1985

The relationship between muscle myosin ATP-ase activity and isometric endurance in untrained male subjects.

The influence of variations in muscle fibre composition on isometric endurance capacity was measured in 23 young healthy untrained male volunteers. After determination of the maximum voluntary force of contraction (MVC), subjects sustained to fatigue contractions at forces of 80%, 50% and 20% of MVC with a 5-min rest between each. A needle biopsy was obtained from m. vastus lateralis and used for histochemical determination of fibre composition based on myosin ATP-ase activity, and fibre are a based on succinate dehydrogenase (SDH) activity. Endurance times were 21 +/- 9 s (mean +/- SD) at 80% of MVC, 56 +/- 17 s at 50% of MVC and 203 +/- 89 s at 20% of MVC. A wide range of muscle fibre compositions was observed with Type I fibres accounting for 48.0 +/- 10.5% of the total, corresponding to 45.0 +/- 11.5% of the total muscle area. Muscle fibre composition, whether expressed as the proportions of the different fibre types present, or as the fraction of total muscle cross-sectional area occupied by each fibre type was not correlated with isometric endurance capacity at any of the three forces studied. Endurance time was also unrelated to MVC. In contrast to the results of previous studies where trained subjects were used, or where different muscle groups were compared, these results suggest that isometric endurance is not influenced by muscle fibre composition.

Adenosine Triphosphatases↗
PubMed1985

Thermoregulation in marathon competition at low ambient temperature.

The 1982 Aberdeen marathon race was held on a cool (12 degrees C) day on a flat, fast course. Fifty-nine of the 750 runners volunteered to take part in this study: rectal temperature of these competitors was measured within 5 min of completing the race. Venous blood samples were obtained before and immediately after the race; body weight of these subjects was also recorded before and after the race. During the race, 200 ml of fluid, either water or a glucose/electrolyte drink, was consumed at each of the seven feeding stations. The mean finishing time of the subjects was 221 +/- 37 min (mean +/- SD, range = 144-307 min). Post-race rectal temperature was 38.3 +/- 0.9 degrees C with a range of values from 35.6 degrees to 39.8 degrees C. The net weight loss was 2.02 +/- 0.72 kg equivalent to 2.9% +/- 0.8% of body weight. The correlation between post-race rectal temperature and finishing time (r = -0.234) was not statistically significant; post-race rectal temperature was significantly correlated with the time taken to complete the second half of the race (r = -0.348, P less than 0.01). No cases of heat illness were seen among the competitors. The results suggest that hypothermia rather than hyperthermia may be a problem for marathon runners competing under these conditions.

Adult↗
PubMed1985

Estimation of plasma volume changes during marathon running.

Indices of fluid loss have been compared in 47 male runners who completed a competitive marathon (42.2 km) race in times varying from 2 hr 37 min to 4 hr 51 min. Body weight was recorded before and after the race; venous blood samples were collected shortly before and immediately after the race and used for the estimation of haemoglobin concentration, packed cell volume and serum concentration of albumin and total protein. All runners drank a total of 1.4 L of water during the race. The mean decrease in body weight was 2.1 +/- 0.8 kg (mean +/- SD), corresponding to 3.0 +/- 1.1% of initial weight. The decrease in plasma volume (PV), calculated from the haematological parameters, was 6.5 +/- 7.8% (P less than 0.001). Serum total protein concentration increased (P less than 0.001) by 10.4 +/- 4.8% and serum albumin (P less than 0.001) by 9.6 +/- 5.6%. The increase in serum protein concentration was correlated (r = 0.64, P less than 0.001) with the calculated decrease in PV, but was greater (P less than 0.001) than could be accounted for by the loss of plasma water. The change in PV varied widely between individuals and was unrelated to running speed. The estimated decrease in total body water (5%) was not different from the decrease in PV (6.5%), suggesting that water losses were evenly distributed between the intracellular and extracellular compartments.

Adult↗
PubMed1985

Rectal temperature after marathon running.

Rectal temperature was measured in 62 male runners who competed in the 1983 Dundee marathon race: all measurements were made immediately after the race. Competitors' times were noted at 5, 10, 15 and 20 miles (8.0, 16.1, 24.1, 32.2 km) and at the finish (26.2 miles, 42.2 km). Mean finishing time of the group was 3 hr 33 min +/- 48 min (mean +/- S.D.; range = 2 hr 17 min-5 hr 11 min). Mean running speed of the group decreased progressively as the distance covered increased. Mean post-race rectal temperature was 38.7 +/- 0.9 degrees C (range 35.6-40.3 degrees C). The post-race temperature was correlated (p less than 0.01) with the time taken to cover the last 6.2 miles (10 km) of the race, but not with the overall finishing time (p greater than 0.05). Only the fastest runners were able to maintain an approximately constant pace throughout the race, whereas the slower runners slowed down progressively. The runners with the highest post-race temperature, although not necessarily the fastest runners, also tended to maintain a steady pace throughout. The runners with the lowest post-race temperature slowed down markedly only over the last 6.2 mile section of the race. The results clearly indicate that runners forced by fatigue or injury to slow down in the latter stages of races held at low ambient temperatures may already be hypothermic or at serious risk of hypothermia.

Adult↗
PubMed1985

Delayed onset muscle soreness following repeated bouts of downhill running.

Perceived muscle soreness ratings, serum creatine kinase (CK) activity, and myoglobin levels were assessed in three groups of subjects following two 30-min exercise bouts of downhill running (-10 degrees slope). The two bouts were separated by 3, 6, and 9 wk for groups 1, 2, and 3, respectively. Criterion measures were obtained pre- and 6, 18, and 42 h postexercise. On bout 1 the three groups reported maximal soreness at 42 h postexercise. Also, relative increases in CK for groups 1, 2, and 3 were 340, 272, and 286%, respectively. Corresponding values for myoglobin were 432, 749, and 407%. When the same exercise was repeated, significantly less soreness was reported and smaller increases in CK and myoglobin were found for groups 1 and 2. For example, the percent CK increases on bout 2 for groups 1 and 2 were 63 and 62, respectively. Group 3 demonstrated no significant difference in soreness ratings, CK activities, or myoglobin levels between bouts 1 and 2. It was concluded that performance of a single exercise bout had a prophylactic effect on the generation of muscle soreness and serum protein responses that lasts up to 6 wk.

Adult↗
PubMed1984

Dehydration and serum biochemical changes in marathon runners.

The effects of a competitive marathon race on serum biochemical and haematological parameters have been evaluated. Blood samples were obtained shortly before and immediately after the race; urine samples were also obtained before and after the race. Body weight was recorded pre- and post-race. During the race subjects consumed a total of 1.41 of either water or a dilute glucose-electrolyte solution. The average weight loss of the runners was 2.09 +/- 0.77 kg (mean +/- SD), corresponding to 2.9 +/- 0.8% of body weight. Small but significant increases in both haematocrit and haemoglobin concentration occurred; plasma volume was calculated to decrease by 4.7%. Serum potassium concentration showed no change, but the response was highly variable; serum sodium concentration increased in line with the decrease in plasma volume. In the group of subjects drinking water during the race, the pre-race plasma glucose concentration was 5.3 +/- 1.2 mmol . l-1, this was unchanged after the race (5.0 +/- 1.2 mmol . l-1). A significant increase (P less than 0.01) in the plasma glucose concentration, from 5.2 +/- 0.6 to 6.0 +/- 1.5 mmol . l-1 occurred in the group of subjects drinking the glucose-electrolyte solution. Apart from this, there were no significant differences between the two groups.

Adult↗
PubMed1984

The relative proportions of fat, muscle and bone in the normal human forearm as determined by computed tomography.

Computed tomography has been used to establish the proportions of fat, muscle and bone present in the normal human forearm. Subjects were healthy young volunteers, eight males and eight females. A series of six cross-sectional scans at right angles to the long axis of the forearm was obtained, the scans being made at equidistant intervals between the olecranon process and the ulnar styloid. The volumes occupied by fat, muscle and bone were calculated for the complete forearm. Total forearm volume calculated by this method agreed closely with that measured by water displacement. For the male subjects, forearm composition was 72.1 +/- 4.4% muscle (mean +/- SD), 15.0 +/- 5.3% fat and 12.9 +/- 1.2% bone. Female forearms had less muscle (P less than 0.001) and more fat (P less than 0.001) than those of the male subjects: 58.5 +/- 4.0% muscle, 29.3 +/- 5.0% fat and 12.3 +/- 1.4% bone. Forearm muscle volume was significantly correlated (r = 0.75; P less than 0.05) with lean body mass in the male subjects; the range of values for lean body mass in the female subjects was too small to permit calculation of the equivalent relationship. Forearm fat content, as a percentage of total volume, was proportional to whole body fat content as estimated from skinfold thickness (males, r = 0.84; P less than 0.01; females, r = 0.77; P less than 0.05). These relationships enable estimates of the volumes of forearm tissue components to be derived from anthropometric measurements.

Adipose Tissue↗
PubMed1984

The influence of variations in muscle fibre composition on muscle strength and cross-sectional area in untrained males.

The force produced by a maximum voluntary isometric contraction of the knee-extensor muscles was measured in a group of fifteen healthy young male volunteers. All subjects were untrained at the time of the study. The cross-sectional area of the knee-extensor muscles was measured at the mid-thigh level using computed tomography. Skeletal muscle samples were obtained by needle biopsy from the mid-point of m. vastus lateralis of the stronger leg of each subject. Samples were mounted, frozen and sectioned for histochemical analysis. On the basis of the pH dependent lability of the myosin ATP-ase reaction, fibres were classified as Type I, Type IIA or Type II B. Using computerized planimetry, muscle fibre cross-sectional areas were measured on serial sections stained for succinate dehydrogenase activity. As previously described, muscle strength (maximum voluntary contraction) was correlated with the muscle cross-sectional area (r = 0.70, P less than 0.01). The ratio of strength (in N) to cross-sectional area (in cm2) was 8.92 +/- 1.01 (mean +/- S.D.) with a wide range of values, from 7.09 to 10.85. Muscle fibre composition of m. vastus lateralis in these subjects was 46.1 +/- 10.5% Type I, 42.8 +/- 11.4% Type IIA and 11.1 +/- 9.7% Type IIB. After correction for differences in the cross-sectional areas of the different fibre types, the proportions of total area occupied by the different fibre types were: 43.6 +/- 11.9% Type I, 46.4 +/- 13.1% Type IIA and 10.0 +/- 9.1% Type IIB. No relationship was observed to exist between muscle strength and muscle fibre composition. Similarly, the muscle strength/cross-sectional area ratio was not related to the proportions of the different fibre types present or to the fraction of the total cross-sectional area occupied by the different fibre types. From the results it can be concluded that there is no difference in the force per unit area which can be generated by the different muscle fibre types present in human skeletal muscle. Variations in muscle fibre composition between individuals cannot, therefore, account for the large variations observed in the ratio of strength to muscle cross-sectional area.

Adult↗
PubMed1984

Muscle strength and cross-sectional area in man: a comparison of strength-trained and untrained subjects.

This study has examined muscle strength and cross-sectional area in a group of 35 healthy untrained male subjects and 8 subjects who had been engaged in a strenuous weight-training programme. The maximum voluntary knee extension force which could be produced by the untrained subjects was 742 +/- 100 N (mean +/- SD). The trained subjects could produce a significantly (p less than 0.001) greater force (992 +/- 162 N). Cross-sectional area of the knee-extensor muscle group was 81.6 +/- 11.8 cm2 in the untrained subjects and 104.1 +/- 12.3 cm2 in the trained subjects (p less than 0.001). In the untrained subjects, a significant correlation existed between strength and muscle cross-sectional area (r = 0.56, p less than 0.001). In the same group of subjects, there was a significant inverse relationship between muscle cross-sectional area and the ratio of strength to cross-sectional area (r = 0.55, p less than 0.001). The mean ratio of strength to cross-sectional area was 9.20 +/- 1.29 for the untrained group whereas for the trained group this ratio was 9.53 +/- 1.01. It is suggested that the inverse relationship between strength per unit cross-sectional area and cross-sectional area results in part from an increased angle of pennation in the larger muscles.

Adult↗
PubMed1984

Whole blood and red cell ATP content in patients with peripheral vascular disease: the effect of cigarette smoking and oxpentifylline.

The relationship between erythrocyte ATP content and the presence of atherosclerotic peripheral occlusive vascular disease was investigated. In 20 elderly patients with severe peripheral vascular insufficiency (10 male, 10 female; age 68.8 +/- 12.5 years; Mean +/- SD) the mean erythrocyte ATP content was 1.57 +/- 0.16 mmol/litre. In a sex and age matched group (69.1 +/- 9.6 years) with no signs or symptoms of peripheral or myocardial ischaemia, erythrocyte ATP content did not differ significantly (1.49 +/- 0.29 mmol/litre). In young healthy volunteers, there was no difference in erythrocyte ATP content between males and females or between cigarette smokers and non-smokers, nor were the values for the young group different from those obtained from the elderly patients. The effect of oxpentifylline administration on erythrocyte ATP levels in patients with peripheral vascular disease was also studied. Administration of oxpentifylline (1.6 g per day in divided doses) over 7 days had no effect on erythrocyte ATP content in 10 patients (5 male, 5 female) with ischaemic lower limbs. These results suggest that measurement of erythrocyte ATP content is unlikely to be a useful index in the assessment of peripheral vascular disease.

Adenosine Triphosphate↗
PubMed1983

A simple one-step enzymatic fluorometric method for the determination of glycerol in 20 microliters of plasma.

An assay for the determination of glycerol concentration in blood or other biological materials is described. The method is based on the conversion of glycerol to dihydroxyacetone in the presence of NAD, the reaction being catalysed by the enzyme glycerol dehydrogenase. The NADH which is formed in stoichiometric quantities during the reaction is estimated fluorometrically. In the presence of the ketone-trapping agent hydrazine the reaction can be made to go to completion above above pH 9.0. Using the method described, glycerol can be measured routinely in a 20-microliters sample of serum or plasma. Although the enzyme is known to react with sorbitol and ethanol, the addition of these substances to the reaction mixture had no significant effect on the determination of glycerol.

Glycerol↗
PubMed1983

Aerobic capacity and fractional utilisation of aerobic capacity in elite and non-elite male and female marathon runners.

The physiology of marathon running has been extensively studied both in the laboratory and in the field, but these investigations have been confined to elite competitors. In the present study 28 competitors who took part in a marathon race (42.2 km) have been studied; 18 male subjects recorded times from 2 h 19 min 58 s to 4 h 53 min 23 s; 10 female subjects recorded times between 2 h 53 min 4 s and 5 h 16 min 1 s. Subjects visited the laboratory 2-3 weeks after the race and ran on a motor driven treadmill at a series of speeds and inclines; oxygen uptake (VO2) was measured during running at average marathon racing pace. Maximum oxygen uptake (VO2 max) was measured during uphill running. For both males (r = 0.88) and females (r = 0.63), linear relationships were found to exist between marathon performance and aerobic capacity. Similarly, the fraction of VO2 max which was sustained throughout the race was significantly correlated with performance for both male (r = 0.74) and female (r = 0.73) runners. The fastest runners were running at a speed requiring approximately 75% of VO2 max; for the slowest runners, the work load corresponded to approximately 60% of VO2 max. Correction of these estimates for the additional effort involved in overcoming air resistance, and in running on uneven terrain will substantially increase the oxygen requirement for the faster runners, while having a much smaller effect on the work rate of the slowest competitors. Five minutes of treadmill running at average racing pace at zero gradient did not result in marked elevation of the blood lactate concentration in any of the subjects.

Adult↗
PubMed1983

The effects of oral administration of salts of aspartic acid on the metabolic response to prolonged exhausting exercise in man.

The effects of the oral administration of salts of aspartic acid on endurance capacity and metabolic responses to prolonged bicycle exercise have been investigated. Previous reports in man and in animals have suggested that this treatment can increase the capacity to perform muscular work by virtue of its effect on circulating ammonia levels. Eight healthy young male subjects exercised to exhaustion on a bicycle ergometer at a work load requiring approximately 75% of maximum oxygen uptake. This work test was performed after placebo administration or after ingestion of 6 g of potassium-magnesium aspartate over a 24-h period, using a double-blind protocol. Exhaustion was reached after 82.7 +/- 23.5 min (mean +/- SD) following aspartate treatment and after 85.4 +/- 26.5 min following the placebo. No differences in the blood glucose, lactate, or ammonia concentrations or in the plasma free fatty acid concentration between the two treatments were observed. The respiratory exchange ratio was the same on both occasions. These results show no beneficial effect of oral aspartate administration on work capacity in man and also suggest that the metabolic processes that occur during exercise are not influenced by this treatment.

Adult↗
PubMed1983

Strength and cross-sectional area of human skeletal muscle.

The maximum voluntary force (strength) which could be produced by the knee-extensor muscles, with the knee held at a right angle, was measured in a group of healthy young subjects comprising twenty-five males and twenty-five females. Both legs were tested: data from the stronger leg only for each subject were used in the present study. Computed tomography was used to obtain a cross-sectional image of the subjects' legs at mid-thigh level, measured as the mid-point between the greater trochanter and upper border of the patella. The cross-sectional area of the knee-extensor muscles was determined from the image obtained by computer-based planimetry. The subjects' height and weight were measured. An estimate of body fat content was obtained from measurements of skinfold thicknesses and used to calculate lean body mass. Male subjects were taller (P less than 0.001), heavier (P less than 0.001), leaner (P less than 0.001) and stronger (P less than 0.001) than the female subjects. No significant correlation was found to exist between strength of the knee-extensor muscles and body weight in the male or in the female subjects. In the male subjects, but not in the female group, there was a positive correlation (r = 0.50; P less than 0.01) between strength and lean body mass. Muscle cross-sectional area of the male subjects was greater than that of the female subjects (P less than 0.001). The ratio of strength to cross-sectional area for the male was 9.49 +/- 1.34 (mean +/- S.D.). This is greater but not significantly so, than that for females (8.92 +/- 1.11). In both male and female groups, there was a significant (P less than 0.01) positive correlation between muscle strength and cross-sectional area. A wide variation in the ratio of strength to muscle cross-sectional area was observed. This variability may be a result of anatomical differences between subjects or may result from differences in the proportions of different fibre types in the muscles. The variation between subjects is such that strength is not a useful predictive index of muscle cross-sectional area.

Adult↗